The Data-Over-Cable Service Interface Specification (DOCSIS®), created by CableLabs research consortium, is an international telecommunications standard that defines interface requirements for cable modems and supporting equipment related to high-speed data transfer and distribution over cable networks. In particular, DOCSIS defines a protocol for bi-directional signal exchange between a cable modem termination system (CMTS) operated by cable service providers and cable modems (at multiple customer premises) over a hybrid fiber-coaxial (HFC) cable plant. Downstream channels from the CMTS can service multiple cable modems through a continuous signal in the downstream direction, while TDMA burst signals in the upstream direction can be received by the CMTS from the cable modems.
A CMTS forms part of a cable company's headend of a cable network and can be connected to the Internet using very high capacity data links to a network service provider (e.g., using Ethernet interfaces). DOCSIS is widely used by cable service providers to offer Internet access through existing hybrid fiber-coaxial (HFC) infrastructures.
A DOCSIS 3.0 implementation entails the CMTS being aware of the HFC topology in the form of the fiber-node configuration that associates a set of downstream and upstream QAM channels (modular or integrated). Many features and functionalities (e.g., Mac Domain Descriptor/upstream ambiguity resolution, load-balancing, spectrum management, etc.) involve HFC topology awareness. In particular, HFC topology information can include fiber node identification, which subscribers each fiber node services, and service group configurations including downstream and upstream channels, and associated ports. When the HFC topology is new or changes, there is a need to ensure that accurate HFC topology information is provided to the CMTS.